Original subtitles

(calm music)

- [Narrator] It covers 1/3 of the world's surface.

Ringed by fire,

constantly reshaped by the almighty clash

of Earth's tectonic plates.

Creating life forms that in turn become the architects

of underwater empires.

Here, the world's most primitive life forms

have outlived dinosaurs

and found astonishing ways to adapt and survive

in one of the most competitive environments on the planet.

(dramatic music)

This is the Wildest Pacific.

The Pacific Ocean sits

atop the world's largest tectonic plate,

over 103 million square kilometers in size.

From deep ocean trenches to the highest mountains,

these plates are the outer pieces of the Earth's surface

that shape our planet's terrain.

Along the edges of the biggest plate is an area

of seismic activity known as the Pacific Ring of Fire.

It's a 50,000 kilometer chain

of volcanoes circling the Pacific.

90% of all earthquakes occur along these lines.

Over millions of years, volcanic archipelagos have formed,

stepping stones for marine life to evolve upon.

Of the Pacific's 25,000 islands,

roughly 2/3 are in the Coral Triangle.

The triangle is a small western Pacific pocket

from Indonesia, north to the Philippines,

and across to the Solomon Islands.

Though marveled for its reefs,

within the volcano-lined bays,

another astonishing ecosystem has emerged.

(bubbling)

This one is less of an underwater rainbow

and more of a fascinating dark cloud.

The muck zones.

Here, creatures thrive in sludge and soot left

from the continental reshaping of eons past.

The ash and minerals that choked many forms of life

have allowed others to bloom here.

Between the volcanic mountains and the bay below

are the protectors of the coastline, mangroves.

Mangroves evolved in the Coral Triangle

long before currents carried their seed pods

to other parts of the Pacific.

This area still grows the largest tracts

of mangrove forests on the planet today.

In a latitude prone to tsunamis and cyclones,

these mangroves absorb wave energy,

shielding the land behind them.

They also protect sea life

by soaking up nutrients from runoff

that could cause smothering algal blooms offshore.

Mangroves have harnessed the unique ability

to survive in water nearly 100 times saltier

than most other plant life.

Their roots sink into the brackish mud for meters.

Here, an entire ecosystem has adapted

to the alien architecture.

Predators can't reach small fish hiding

behind the fence of roots.

These are forests that live between tides

and so too do many of the animals.

Mud burrowers forage at low tide

and hide at high tide.

Small sand crabs, like these fiddlers,

help stimulate the turnover of nutrients

on the mangrove flats.

They feed the mud into their mouth parts

and filter algae and bacteria from it.

They then spit out

and deposit the remaining unusable sand back on the ground.

Rather than leaving a messy trail in its feeding wake,

the deposits are left as perfectly formed balls

called feeding pellets.

One claw of a male fiddler crab is so enlarged,

it actually impedes feeding.

Bright orange and red, he uses his claw to guard a burrow

and try to catch the attention of a passing mate.

The ultimate mangrove grazer is one

that can take full advantage of both low and high tides.

This is a fish that does exactly that.

The mudskipper breathes air and walks on land.

It spends up to 90% of its life above the water line.

It retains water in its gills.

But the fish's skin has also adapted

to absorb oxygen directly from the air.

Mudskippers can survive out of water

for up to 36 hours this way.

Their eye lenses have flattened out,

so while they see clearly on land,

their underwater vision is clouded.

An additional fin segment, not found in most swimming fish,

has effectively created a shoulder for the mudskipper,

allowing it to use strong pectoral fins

to drag itself across the mud

and virtually walk on water.

(water splashing)

These archers have also evolved eyesight differently

to most fish.

Binocular vision allows archer fish

to see through a distorted water surface

and gauge distance beyond.

They're looking for small insects and crabs resting

on the mangrove roots.

A channel runs from the back of their throat

to their mouths, which effectively acts as a water pistol

to target prey above the water line

and gobble up the wounded as they hit the water's surface.

Archer fish have adapted so well as mangrove hunters,

they rarely leave.

But many others do.

Mangroves are reef nurseries.

Some species spawn upstream,

knowing the coastline will provide sanctuary

for juveniles not yet big enough

to survive the harsh reef city life.

When it's time to graduate from the nursery,

other habitats grow just offshore

that allow enough cover for a first foray into ocean life.

Often mistaken for seaweed,

seagrass is more closely related to a terrestrial plant.

Whereas generally accepted most life came from the ocean

and eventually moved to land,

seagrass migrated in reverse.

Coastal grasses adapted to salt around 100 million years ago

and gradually moved further into the seas.

They have roots, stems, and leaves,

and produce flowers and seeds.

Like their land-based cousins,

they depend on sunlight to photosynthesize.

Seagrass is a vital food source for large marine grazers.

Dugong, shore birds, and sea turtles.

The grass roots extend into the sediment.

Here they anchor the plant, absorb and store nutrients,

and hide small burrowers.

There are 60 seagrass species.

They spread far and wide across the Pacific

with the help of turtles.

The green turtle adults are herbivores.

They rely on the seagrass and keep meadows at healthy levels

with constant mowing.

In return, they travel hundreds of kilometers

to new feeding areas,

with grass seeds as tiny passengers on board.

The turtles will digest and pass the seeds,

sowing new grounds.

Elsewhere in the sea grass,

an anemone has anchored away

from the bustling coral civic center,

where there's less competition for space.

An animal closely related to coral polyps and jellyfish,

the anemone has a foot disc that attaches to a hard surface.

And like many other species,

this one sees the real estate value

in setting up shop away from the busy reef,

near a seagrass patch.

Anemones in sparse areas like this become satellite suburbs.

A saddleback clownfish family has moved into this one.

Saddlebacks often take up residence away from the reefs.

They're born with a thick protective mucus

to afford some immunity from the anemone's stinging arms.

The clownfish adds to this coat as they grow.

They brush up against the host's tentacles

until the protective coat is roughly four times thicker

than the average fish.

The anemone isn't so kind to other species.

It uses harpoon-like nematocysts

to paralyze prey passed to a central mouth.

It absorbs the nutrients

and spits out the parts it can't digest, shell and bone.

In return for sanctuary,

the saddleback provides the anemone

with another food source in the form of waste

and chases away predators like butterfly fish,

which have developed a taste

for the nutrient-rich anemone flesh.

Though few can withstand the anemone's firing nematocysts,

there's still competition for this prime real estate.

The anemone shrimp isn't immune to the animal's sting.

It acclimatizes through a long process of gradual contact,

which can take up to five hours.

When the host is used to its new visitor,

it will allow the shrimp to walk around unimpeded

and feed from the anemone's skin.

Another visitor is the tiny spotted porcelain crab.

It uses the anemone as a safe place

to launch its own evolutionary spectacle, fans.

This filter feeder isn't a true crab.

It's evolved much like one in shape

but it's more akin to a flattened lobster.

It's grown feathery arm-like appendages from its mouth,

designed to cleverly net plankton.

Porcelain crabs rarely share

the same anemone with clownfish.

But in a seascape with little other protection,

these small colonizers have learned to coexist.

The saddlebacks lay their egg clutches

as close as possible to the protection of the stinging arms.

The male clowns are charged with guarding the eggs.

He gently aerates the eggs by fanning them

and picks out the unfertilized ones.

Nearby, the seagrass is providing cover

for another nesting site.

Bigfin reef squid.

The male bigfin flashes colors

to attract the attention of a passing female.

When he's successfully mated,

he will dutifully stick around to guard the female

while she lays her clutch.

Small barracuda, yet to graduate to the outer reef zone,

lie in wait at the seagrass edges.

Other male squid are on the lookout

for females of their own.

The egg capsules will take two to three weeks to hatch

before several hundred tiny squid larvae emerge

to join the planktonic slipstream.

Despite their union for the egg-laying process,

the parental squid won't be around

to defend their young when they hatch.

Squid have short lifespans

and usually die not long after mating.

These bigfin live out their entire life cycle

in just under a year.

Seagrass predators aren't limited

to patrolling the perimeters.

Danger can also appear from below.

On the rising tide,

bluespotted ribbontail rays cruise the seagrass flats.

Gel-filled pits across the front of their faces allow them

to pick up electrical signals from the tiniest movement.

Much like the terrestrial life

that exists just below a rainforest floor,

worms and crustaceans consume decaying leaves

that line the seagrass beds.

The ribbontail ray pinpoints activity,

vacuums up the morsels, and crushes them

between specially adapted mouth plates in mere seconds.

By the end of entree,

the ray is hidden just below the surface,

with eyes perched atop to scour the sea floor

for the next course.

(dramatic music)

Free swimmers, like the razorfish,

have gone to extraordinary lengths to blend in.

The razorfish swims head down

and backwards in dense schools,

in an effort to mimic the blades of grass it shadows.

Many bottom dwellers, like this eel snake blenny,

have taken on vivid greens in an effort not to be seen.

A finger dragonet will raise its elongated green top spine

at full mast to mimic a blade of grass.

In some species, these spines are tipped

with a further deterrent, venom.

One animal that rarely deigns to attempt camouflage is

the aptly named flamboyant cuttlefish.

Growing no longer than eight centimeters,

a living specimen of the flamboyant wasn't discovered

until the late 1980s.

This cuttlefish puts on a dazzling color display,

shimmering through a range of vibrant yellow,

maroons, and white.

And amazingly, it walks.

The cuttlebone that helps with buoyancy in most cuttlefish

is relatively small in the flamboyant.

It can't propel very fast or for very long.

It's adapted two front clubs to tread along the sea floor.

Pulsating skin alerts predators to a poisonous secret.

Its flesh is highly toxic.

The flamboyant cuttlefish tests the full gamut

of its color range when hunting for small squid and crab.

It can send waves of color along its body.

It's thought in an attempt to hypnotize prey.

Or it may lighten to color match its surroundings,

to tone down slightly right before

a strike.

This tiny cuttlefish has twin tentacles it uses for hunting.

It launches them together as a single spear

with deadly accuracy.

With hunters stalking the seagrasses,

it's a wise decision to hail transport.

Imperial shrimp are brightly colored

and just a couple of centimeters long.

To ensure safe passage from one area to another,

they frequently catch a lift on a nudibranch,

a colorful type of sea slug.

Or they may choose to travel by sea cucumber,

a long worm-like animal related to starfish

with a mouth surrounded by tentacles.

Both the nudibranch and sea cucumber are shell-less

and often toxic, therefore ignored by most predators.

In return, the hitchhikers conduct a quick house clean,

eating algae and parasites.

Usually spotted in pairs,

they'll squabble over the best patches

until they arrive at new feeding areas.

There are 14 seagrass species in the Coral Triangle bays,

along with a number of seaweeds.

This macro algae is Halimeda.

Halimeda is generally found in bays and inshore of reefs.

It's made up of calcific plate-like segments.

When it breaks down, it becomes calcium carbon sediment,

or simply sand.

Halimeda has a very rapid growth rate,

which means the sand in many Coral Triangle bays

can be attributed more to the Halimeda fields

than the reef itself.

Unlike seagrass, Halimeda doesn't have roots

sinking into the sea floor.

It attaches to rocks and hard surfaces.

Visual predators can hunt easily in the scant cover,

so these algae gardens have produced

some astonishing adapters.

Fish and crustaceans that bend and blend

into the Halimeda itself.

Ghost pipefish are master mimickers.

The Halimeda ghost pipefish takes on the green, red,

or brown of the algae it descended on as a tiny larva.

It's a close relative of the seahorse.

But like the Halimeda,

this fish is covered in large bony plates.

It swims mouth to floor,

sucking up tiny mycid shrimp with its tube-like mouth.

It barely merits a second glance

when it's suspended next to the macro algae

that pipefish's entirely physiology is based on.

It's not the only pretender in the Halimeda kingdom.

At just three centimeters long,

this tiny crab is a perfectly proportioned bite

for a lagoon carnivore.

Stingrays, eels, and octopus.

To blend in, it's developed a long bright green shell.

But that's just step one of the deception.

The Halimeda crab will pinch off segments of growing algae

and affix it to its head with the help of tiny hooks.

The top-heavy weight can cause it

to stagger slightly in the current,

which only adds to the illusion

of a plant swaying in flowing water.

The Halimeda algae itself is a food source.

This minuscule sap-sucking slug feeds on the plant

and ingests chloroplasts into its body as it does so.

Incredibly, it then photosynthesizes

the absorbed plant matter.

It can live for months without food this way,

essentially becoming a solar-powered slug.

The finer details of just how they're able to do this

are still being researched as new species are uncovered.

This one feeds on a close Halimeda cousin,

the toxic sea grape,

and has taken mimicry to a new level.

(calm music)

Sea urchins slowly crawl along the open plains of Halimeda.

Long sharp spines discourage hunters

and of the 200 odd species of urchin,

some also wield spikes filled with venom.

They're the ideal hiding place for young cardinal fish.

The male cardinals take on the primary parenting role,

in the early days at least.

They are mouth brooders.

They keep the eggs and hatchlings in their mouths

for up to three weeks.

When the baby fish, called fry, are ready to leave,

the male will find a spiny nursery.

He delivers them to the safety of a sea urchin's spines,

where they can grow further

before graduating to coral reefs.

The sparse vegetation also invites sand burrowers.

This giant goby lacks the ability to dig,

so it's struck up one

of the bay's more unusual partnerships.

The snapping shrimp is blind

but is happy to pay for the services of a watchman.

The shrimp spends the best part of its day

tirelessly digging a burrow.

It shares its home with a giant goby,

which has evolved large pectoral fins

to sit stop the burrow lip and keep watch.

Gobies have excellent eyesight.

Remarkably, fish and shrimp have developed their own system

of interspecies communication.

The shrimp will only emerge from the hole

after extending an antennae and touching the goby's fin.

It waits for a wiggle to let it know the coast is all clear.

The goby will vary its wiggle signals

to the shrimp throughout the day

to keep it up to date with the danger levels.

(dramatic music)

While it's working outside of the burrow,

the shrimp never loses contact with a goby.

At all times, one antennae is touching the goby's body.

In the late 1980s,

Indonesia's dive expedition industry began to flourish.

With it, reports of a small brightly-banded octopus,

not seen anywhere else before,

started to trickle back to scientific circles.

It wasn't until 2006

that the wunderpus photogenicus was officially described.

With identifying head markings

as unique as human fingerprints,

the rare wunderpus has fast become a darling

of the dive world in unique areas known

as the Coral Triangle's muck zones.

Muck zones are covered in silt and mud.

They seem unlikely areas to support life.

Bordered by volcanoes, many Coral Triangle bays are made up

of black sand, remnants of pulverized rock and ash.

The ash is mineral-rich,

but the resulting sludgy sediment forces animals

to adapt or die.

The sludgy sediment can smother the symbiotic algae

living in coral reefs.

Without these foundations,

muck zones are not an easy place for organisms to thrive.

However, the harsh conditions have forced some

of the bay's most unusual adaptations.

Ambush predators and highly skilled camouflagers

have learned to take advantage of the slightest cover.

This frogfish is just a few centimeters long.

Frogfish species vary in color and texture.

They're very good at blending in.

But this brightly colored painted frogfish

is equally confident slowly making its way

through the muddy wasteland.

It has specially adapted fins it fans out like feet.

It can walk or push into a glide.

However, frogfish aren't exactly ergonomically designed.

They have rounded faces

and their tails are often shoddy rudders,

curving to the side.

Moving about can be a slow and awkward process.

This fish can even use its fins much like hands

to anchor itself in place

when the current gets to be too much.

At this pace, it's hardly surprising

that the frogfish doesn't chase down its prey.

Instead, it's come up with an ingenious plan

to tempt passersby to come in a little closer.

The front dorsal fin has evolved

into a form of fishing rod,

a long spine with a bulb on the end.

Much like a fishing fly,

the frogfish will deploy the lure

and twitch it to see what comes out of hiding.

An ambitious cast.

The escaping lizardfish

was nearly double this frogfish's size.

Other species have also adapted their bodies

in strange ways.

This stony gargoyle is a demon stinger fish.

Like many slow movers, it's tipped with venomous spines.

It has no known natural predators.

Its ghoulish reputation is clinched by these.

Hooks either side of the fish sink into the muck

and drag the fish along the floor.

Their modified spines long ago detached

from the rest of the pectoral fin.

As a larvae, this leopard flounder presents

much like a free swimming fish,

with eyes on either side of its head.

But as it grows, its body flattens out

and one eye slowly migrates to the top.

It can now settle into the sea floor

with in-built periscopes

that keep a 180 watch for incoming predators.

Like dolphins.

However, the flounder has an unusually shaped mouth.

Unlike its eyes, it didn't quite make the migration

from a free swimming juvenile to floor-dwelling flatfish.

The sideward gape, a vestige of evolution in progress.

Another variety of flatfish, the banded sole,

has poisonous glands at the base of its fins.

However, this is not a banded sole.

It's a mimic.

The mimic octopus.

The mimic octopus is a cephalopod, a suborder of mollusks.

With the exception of the nautilus,

most cephalopods abandoned shells

around 100 million years ago,

forcing them to specialize in other defense techniques.

A squid has speed.

Cuttlefish blend.

This small brightly-banded octopus

has developed a novel method

for crossing the sparse muck flats.

It pretends.

Gliding across the sea floor,

it flings all eight arms behind and undulates,

copying the movement of the toxic sole fish.

And if that doesn't work,

a predator will think twice before wrestling a lionfish.

It's thought this display mimics the feathered fins

of one of the muck's deadliest stingers.

These shapeshifters were only spotted

off the Indonesian coast in 1998.

At last count, the mimic octopus's repertoire includes

more than 15 shapes.

From sea snakes to starfish.

And if all else fails,

it can bury itself below sand in seconds.

Other masters of muck mimicry are these, decorator crabs.

The name encompasses a broad number of species.

Some are hermit crabs, crabs with soft bodies

that live in the abandoned shells

of sea snails for protection.

Others grow with their own exoskeleton.

But the common trait of a decorator is

to add a few extra items to their shell or carapace.

This spider crab picks up small stones

from its algae-covered surrounds

and uses tiny hooks to affix the pebbles to its back

and legs, giving it a jewel-encrusted appearance.

Others will use anemones, small stinging animals

that have the added benefit of packing a toxic punch

if a predator comes too close.

Some decorators simply pick up whatever is closest to hand

and hang on for as long as the costume holds together.

This leaf from the jungle above also makes

for a perfect hang glider in the current.

There are few places on Earth

where the reef touches the doorstep of the jungle.

When these ancient ecologies collide,

a specific muck zone emerges.

Tree stumps and leaves line the bay shallows.

Here, nothing goes to waste.

Life has learned to use the offerings from the world above

for nests and refuge.

Rotting vegetation provides nutrients.

Fallen leaves retain stored carbon

and redistribute it into the sea floor.

Many of the animals adopt a specific camouflage dress code.

Be like the leaf.

The cockatoo waspfish comes in varied autumnal colors

of decaying leaves.

But this fish takes leaf mimicry one step further.

It's a terrible swimmer.

In a fiercely competitive habitat,

that could appear to be an evolutionary mistake.

However, there's no room for such missteps in the muck.

The cockatoo waspfish has developed an elongated dorsal fin

that peaks highly on his forehead.

It's a rudder.

The waspfish sways in the prevailing current.

And when it sails at full mast, simply lifts into it

like a leaf caught in the tide.

If the ruse isn't convincing,

the dorsal fin is tipped with venom.

So are the spines of this leaf scorpionfish.

It's a masterful ambush predator.

It allows the leaf mimic to hide in plain sight.

Another ambush predator prefers to bed down into the muck.

A stargazer has a wide mouth

and large eyes to look upward for the passing meal

that will soon be drawn out by dusk.

An octopus does some housekeeping before the day's end.

They have several layers around their territory,

so there's always an escape bolt hole nearby.

This one, at the base of a coral bommie,

appears to be its preferred dining room.

The outskirts are lined with the remnant shells

and carapaces of meals past.

An octopus's garden.

As the jungle above prepares for the evening,

dusk too heralds a changing of the guard below.

Fire urchins, usually solitary as they roam the muck floor,

begin to amass.

Little more than a mouth and gut,

they move about on hundreds of tiny feet.

Once a year, they come together for a ritual,

to ensure the continuation of their species, to spawn.

Resident cardinal fish,

living in the protection of the urchins' spines, merge,

creating a super school cloud above the writhing mass.

The urchins will only come together this way

when water conditions allow the best odds

to carry the sperm and eggs out to open water.

The en masse release gives the cloud the best chance

of surviving long enough to fertilize.

How they communicate to each other

that tonight is the night is unknown.

The bigfin squid is also laying the last of her egg clutch.

She too knows it's a numbers game.

Few of the emerging baby squid will live to adulthood.

This female flamboyant cuttlefish needs all the protein

she can capture tonight.

She's looking for a place to lay eggs.

She's found it in the shell of a coconut,

a gift from the Papua New Guinean jungle.

The opening leaves just enough room

to allow the tiny cuttlefish to push her eggs inside.

She lays the eggs one by one but will carefully deliver

up to two dozen perfectly round pearls

into the coconut shell.

It's the safest place she can find for them

but to be sure, she'll spend the coming weeks close by,

protectively guarding it.

Clouds of tiny juvenile fish begin swarming

to take advantage of the cover of darkness to feed.

A leopard anemone extends its arms into the moonlight.

It appears to be safe harbor in the vast seagrass beds.

But at night, the ocean floor comes alive.

The muck food chain is triggered into action.

For the leopard anemone,

there are just a few precious hours to feed.

Its tentacles grasp and stun anything

that ventures too closely.

The water is so thick with schooling juveniles,

the yellow frogfish doesn't even need to deploy its lure

to bring them into striking distance.

Six milliseconds.

It's the fastest strike rate of any living vertebrate.

(gentle music)

The moon is also a cue for life to awaken.

It's time for the flamboyant cuttlefish to hatch.

They incubate in their egg sacks for about 50 days.

Inside, minuscule fully-formed versions of the adults,

just millimeters long.

The adult parent usually dies before the eggs hatch.

The babies are on their own.

However, these cuttlefish emerge

with all of their superpowers ready to be unleashed.

They switch on the skin chromatophores

that allow them to change color

and flash their poison alarm to predators.

They will also immediately hunt.

The newly emerged cuttlefish will drift off

into the slipstream of tiny planktonic forms

that make up the lowest rungs of the food chain.

The muck zones of the Coral Triangle bays

are an astonishing ecology,

born from the depths well below the Earth's crust.

Right across the Pacific Ocean,

the slow grind of tectonic plates marches on,

giving rise to new geological formations

and the surprising life forms that find a way to adapt

in every corner of the ocean.

(calm music)